You won't ever be 'rid' of them to be honest, not if your dd is susceptible. Some children just get them if they're going round, some don't. (Just like some people don't get eaten alives by midges in the summer, and some, like me, do).
You need the nitty gritty. It needs to be part of your hair washing routine.
You will still get the odd one, catch the odd egg, but you'll avoid infestation - and really, thats the nasty thing, the occassional nit/egg, caught with a nitty gritty is not something to be overly concerned about, you're still catching the buggers before they breed.
I spent a fortune on lotions and potions, repellents and strange old wive's tales, but nothing stops them if you're going to get them, you will.
So, nitty gritty is a nit management device really.
When you've washed yor hair and your dd's, just use a fair amount of regular conditioner, nitty grit comb through, if you catch one, then section the hair and be more thorough, but usually just a comb through will tell you if there are any in there.
We've gone from regular breeding grounds to probably one single egg found every other month.